Reading the Rain in Rocks: A late deglacial speleothem record from Sumatra, Indonesia

• Main Author: Wurtzel, Jennifer Beth
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Canberra, ACT : The Australian National University
• Subjects: paleoclimate; palaeoclimate; speleothem; geochemistry; oxygen isotopes; tropical climate; moisture source; Indo-Pacific; IPWP; Younger Dryas; ITCZ; intertropical convergenzce zone; deglaciation; Pacific; Indian; North Atlantic
• Online Access: http://hdl.handle.net/1885/143191; https://doi.org/10.25911/5d51441bb2191; https://openresearch-repository.anu.edu.au/bitstream/1885/143191/5/Wurtzelthesis2018.pdf.jpg

The Intertropical Convergence Zone (ITCZ) is a key component of Hadley cell circulation. In the Indo-Pacific Warm Pool (IPWP) region, the seasonal migration of the ITCZ defines much of the precipitation variability over the Maritime Continent. The seasonal migration of the ITCZ in this region is also closely related to the Australasian monsoon, which brings critical rainfall to Asia and Indo-Australia, cumulatively home to approximately 40% of the global population. On interannual timescales, rainfall in the IPWP region is also connected with zonal climate variability of the El Niño-Southern Oscillation and Indian Ocean Dipole systems. Understanding the IPWP’s climate sensitivities is therefore crucial to the improvement of long-term prediction of rainfall and drought. Abrupt changes in Atlantic Meridional Overturning Circulation (AMOC) are known to have affected the strength of the Asian monsoon during glacial and deglacial climate states. However, there is still much uncertainty around the hydroclimate response of the IPWP region to abrupt climate changes in the North Atlantic. Speleothems are powerful archives for paleoclimatic reconstruction, providing absolute-dated and often highly-resolved records of past climate. Several speleothem oxygen-isotope (δ18O) records from the central IPWP and Asian summer monsoon regions provide decadally-resolved time-series of past rainfall variability since the last glacial period. Many studies have suggested a southward shift in the ITCZ in the IPWP region during phases of reduced AMOC. However, existing IPWP proxies have seasonal biases and conflicting responses, making it difficult to determine the true extent of North Atlantic forcing in this climatically important region. In Chapter 2 of this thesis, I present a precisely-dated, high-resolution record of eastern Indian Ocean hydroclimate variability spanning the last 16 ky (thousand years) from δ18O measurements in an aragonite-calcite speleothem from central Sumatra. This represents the western-most speleothem record ...